296-202 Physical Geology

What is Geology?

Basic Sciences

The sciences that set the general principles for all the other
sciences

Mathematics - "The Rules"

Physics - "The Board

Chemistry - "The Pieces"

Megasystem Sciences

The sciences that describe the great systems that make up the
Universe

Astronomy - Stars and Galaxies

Geology - Planets

Biology - Life

Possibly:

Psychology - The Mind

Sociology - Social Communities

Specialty Sciences

Sciences that examine some smaller, more manageable part of
the Basic or Megasystem Sciences

Zoology

Botany

Meteorology

Mineralogy

.....etc.

Geology Relates to all other Sciences

Physics

Geophysics

Seismology

Interdisciplinary

Historical Geology

Economic Geology

Structural Geology

Hydrology

Oceanography

Geomorphology

Chemistry

Mineralogy

Petrology

Geochemistry

Astronomy

Planetary Geology

Biology

Paleontology

Paleo-

ecology

botany

climatology

....etc.

Who Geoscientists Are:

About 30,000 in the U.S.

Globally, in rich and poor countries, about one per $50
million GNP.

Mostly male but changing rapidly (now about 25% female in
U.S.)

Still less than 10% minority in U.S. (moving up slowly)

Where Geologists Work

40 % Private Sector

30 % Academic

30 % Government

What Geologists Do:

Locate Geologic Resources

Geologic Hazard Mitigation

Geological and Mining Engineering

Site Study

Land-Use Planning

Environmental Protection

Environmental Impact

Ground Water and Waste Management

Basic Research (Furnishes fundamental knowledge for the
applications)

Some Unique Aspects of Geology

Importance of Relationships

Sequential

Spatial

Importance of Time

Some Geologic Rates

Cutting of Grand Canyon

2 km/3 m.y. = 1 cm/15 yr

Uplift of Alps

5 km/10 m.y. = 1 cm/20 yr.

Opening of Atlantic

5000 km/180 m.y. = 2.8 cm/yr.

Uplift of White Mtns. (N.H.) Granites

8 km/150 m.y. = 1 cm/190 yr.

Movement of San Andreas Fault

5 cm/yr = 7 m/140 yr.

Growth of Mt. St. Helens

3 km/30,000 yr = 10 cm/yr.

Deposition of Niagara Dolomite

100 m/ 1 m.y.? = 1 cm/100 yr.

At 1 Second = 1 Year:

35 minutes to birth of Christ

1 hour+ to pyramids

3 hours to retreat of glaciers from Wisconsin

12 days = 1 million years

2 years to extinction of dinosaurs

14 years to age of Niagara Escarpment

31 years = 1 billion years

Distinctive Problems of Evidence

Slow Rates

Rare Events

Destruction of Evidence

Inaccessibility

Reliance on Inference and Deduction

Intrinsically "Unsolvable" Problems

Ancient Landscapes

Mass Extinctions

Ancient Ocean Basins

Scientific Principles in Geology

Parsimony (K.I.S.S.)

Superposition

Uniformitarianism

Using these, plus observation, we establish facts about Earth
Processes

Superposition

A Whodunit? Last night one of Green Bay's premier beer
can collections was stolen. The only clues are tracks in the snow.
We know the last person leaving the scene was the thief. Below:
the evidence and the suspects

The Butler walks to work

The
Handyman rides a bike

The Cook rides a motorcycle

The Maid drives a car

The Nephew has a seeing-eye dog

If you ever watch mysteries nowadays, you know the butler never
does it any more. But if one of the dog's footprints had not
chanced to overlap the butler's, we would not be able to tell
which of the two went last. That often happens in geology - you
can't always tell which of two events happened last, and often
having the critical evidence is a matter of chance.

Contacts

Contacts between rock bodies are where we find the critical
information about time relationships. Below is a hypothetical
view of a cliff. The colors and patterns are commonly used in
geology. The green lined beds are shale, the blue brickwork
denotes limestone, and the yellow stippled rocks are sandstone.
The red is an intrusion and the gray is a fault.

The order in which the rock layers formed is obvious: those on
the bottom formed first. The intrusion has to post-date at least
the uppermost layer it intrudes. Intrusions often alter or bake
the adjacent rocks (dark tones) and include chunks of them.

The fault shown here is actually more realistic than the
simple lines shown in most illustrations. Generally faults are
zones of fractured and crushed rock rather than simple clean
planes. Now how do the rocks left of the fault relate to those on
the right? We can't tell. Nowhere right of the fault do we find
sandstone bounded above and below by shale. So we'll have to go
elsewhere to find out. The logical way to sort out data gathered
at widely separated localities is to plot it on a map. Obviously
the fault is later than all the rocks it cuts.

What about the fault and the intrusion? Here we'd have to get
up close to the fault and look. If the intrusion baked the rocks
in the fault zone or cut across parts of the fault, we'd conclude
the intrusion was later. If there were bits of the intrusive rock
included in the fault zone, we'd conclude the fault was later.